The invention relates to a clip used to create a concertina shaped barrier by connecting adjacent loops of a coil of helical barbed tape.
Helical barbed tape is widely employed as an elongated antipersonnel barrier that may be staked to the ground to define a perimeter, installed at the base of a fence, or mounted on the top of a fence, a wall or a rooftop. The typical helical barbed tape comprises an elongated helically formed central support from which spaced apart clusters of barbs extend. Each cluster of barbs typically comprises a total of four barbs, with a first pair of barbs extending from a root on the radially inner side of the central support and a second pair of barbs extending from a second root on the radially outer side of the central support. Each barb is an elongated generally flat member having opposed converging edges which intersect at a very sharp point. Helical barbed tape is shown in U.S. Pat. No. 3,463,455 which issued to Meckel on Aug. 26, 1969 and is entitled "HELICAL BARBED TAPE UNITS."
One variation of a helical barbed tape product of a general type is manufactured by first roll forming a longitudinally extending barbed tape around a reinforcing wire, and then roll forming the combined tape and reinforcing wire into a helical configuration. A barbed tape product of this type is shown in U.S. Pat. No. 2,908,484 which issued to Uhl on Oct. 13, 1959 and is entitled "BARBED WIRE SPIRAL." In U.S. Pat. No. 2,908,484 the adjoining coils of barbed tape are clipped together at spaced apart intervals to define a barbed tape concertina.
Several improvements have been made in the apparatus and process for manufacturing helical barbed tape products. For example, U.S. Reissue Pat. No. Re. 30,814, which reissued to Michael R. Mainiero on Dec. 8, 1981 entitled "APPARATUS AND METHOD FOR FORMING BARBED TAPE" discloses a machine and a method for making a coil of barbed tape from substantially linear metal stock. The in-line method for forming barbed tape, as disclosed in U.S. Reissue Pat. No. Re. 30,814, simplified manufacture of a coil of metal tape in an in-line mass production operation, with the resulting product being closely compacted helical coil which is suited for extended field use as an antipersonnel barrier. The helical barbed tape that is depicted in U.S. Reissue Pat. No. Re. 30,814 is formed from an elongated strip of metal stock which is stamped and then edge bent into identical segments of equal length which are offset at an exact bend angle relative to a trailing edge segment, thereby forming the tape into an annular coil having a continuous succession of identical adjoining segments. The edge bending process creates periodic folds in the central supporting portion of the coil at a juncture between identical straight line segments of the barbed tape. The folds result in an abrupt change in the cross section of the barbed tape, thereby causing stress concentrations located on the radially outer edge of the fold and in areas along both sides of the fold. The area located on the radially outer edge of the fold is affected by tensile stress caused by the stretching of the radially outer portion of the tape during the edge bending process, whereas the areas along either side of the fold are affected by compressive stress caused by the buckling of the radially inner portion of the tape during the edge bending process.
The concentrations of stress that arise proximate to the fold may promote the formation of microscopic cracks and fissures in the material. The propagation of such a crack or fissure, which can be caused by constant exposure to high winds, windswept sand, heavy rains, or below freezing temperatures, would most likely result in a failure of the material over extended periods of time, thereby compromising the security of the facility that the barrier is intended to protect. A further stress related failure can occur if the helical barbed tape is improperly installed on the top of a fence or wall. In particular, the tape may be forcibly manipulated into an undesirable configuration, thereby introducing additional stress to the material in the regions of the folds.
U.S. Pat. No. 4,503,423 which issued to Joseph J. Mainiero et al., on Mar. 5, 1985 entitled "EXTENSIBLE AND RETRACTABLE BARRIER AND ELECTROMAGNETIC INTRUSION DETECTOR THEREFOR," discloses a single coil structure wherein adjacent loops of helical barbed tape coil are welded to one another at a plurality of spaced apart locations about each loop to achieve a desired concertina configuration. In U.S. Pat. No. 4,503,423 the weldments between the adjacent loops on the barbed tape permanently secures opposed major surfaces of adjacent turns of the coil in abutting face-to-face surface contact. The resulting connection prevents longitudinal, radial, and pivotal motion of adjacent turns relative to one another at the attachment points. The rigid and permanent weldment of adjacent coils at a plurality of such attachment points defines a concertina-like structure which is intended to prevent intruders from passing between adjacent coils.
In a common thirty three loop, thirty inch concertina configuration of helical barbed tape, such as that described in U.S. Pat. No. 4,503,423, there are approximately one hundred welded connections, each loop having three designated attachment points. It is essential to weld each of the adjacent loops of the helical barbed tape in a specific pattern or the concertina configuration will be compromised. Therefore, if adjacent coils of helical barbed tape are inadvertently welded at a location other than the required attachment point, the entire barrier will have to be discarded because the welded connection is permanent. Furthermore, the heat associated with the welding of adjacent loops of coil may cause a local weakness or damage to the helical barbed tape.
U.S. Pat. No. 4,906,975 which issued to Casella et al., on Mar. 6, 1990 entitled "VIBRATION RESPONSIVE INTRUSION DETECTION BARRIER," discloses an intrusion detection barrier comprising inner and outer coils defined by helical barbed tape. The inner coil includes a vibration sensitive electrical cable and is supported centrally within the outer coil by radially extending supports or straps. In particular, U.S. Pat. No. 4,906,975 discloses a radially extending support strap comprising an elongated strip of metal, having been bent into a generally J-shaped structure about an axis orthogonal to its longitudinal axis, to define an elongated support section, a small arched region, and an engaging flap. The radially outer end of the elongated support section and the engaging flap both include identical circular apertures extended therethrough and symmetrically opposed. The radially outer portion of the elongated support section, the arched region and the engaging flap are deployed about two contiguous outer coil loops of concentric helical barbed tape at the folded juncture between two edge bent segments. The circular aperture disposed in the engaging flap is intended to make contact with the fold on the segment bent helical barbed tape, thereby minimizing pivotal motion at the connection point. The circular aperture disposed in the radially outer end of the elongated support section of the strap is intended to promote the proper nesting of adjacent coil loops during storage. To secure the two contiguous outer loops of concentric helical barbed tape together, the radially inner distal end of the engaging flap is spot welded intermediate the elongated support section, thereby permanently connecting the adjacent loops of helical barbed tape at a plurality of juncture points between two identical edge bent segments about the circumference of the coil to form the desired concertina configuration. Despite the desirable features found in U.S. Pat. No. 4,906,975 it is desired to provide significant advances in clip means for connecting adjacent coils of helical barbed tape to form a desired concertina configuration.
Accordingly, it is an object of the subject invention to provide a new and improved clip for connecting two adjacent coils of segment-bent helical barbed tape in a concertina configuration in a manner to reinforce the stressed regions along the radially outer edges of the contiguous folds as well as along either side of the contiguous folds.
It is an additional object of the subject invention to provide a clip with a unitary mechanical locking system which can be removed from adjacent loops cf helical barbed tape in the event that the clip was inadvertently connected at an undesirable location.
It is a further object of the invention to provide an unformed clip blank that includes stamped reinforcing apertures and a unitary locking system, which can be loaded into a magazine on an automatic installation gun and quickly installed on adjacent loops of segment bent helical barbed tape to form a concertina configuration.